Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin

Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

We were lucky to be able to fish through this storm as it skirted around us to the north, giving us just enough clouds to prompt a BWO hatch but keeping the lighting at a safe distance.

From Slough Creek in Wyoming

Stream photos

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Female Skwala (Large Springfly) Stonefly Adult Female Skwala (Large Springfly) Stonefly Adult

Lateral view of a Female Skwala (Perlodidae) (Large Springfly) Stonefly Adult from Mystery Creek #308 in Washington

9 Recently Added Photos

27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

proteus, biloba, and comstocki

Pteronarcys biloba (Knobbed Salmonfly) Stonefly Nymph

17 Pictures

Dorsal view of a Pteronarcys biloba (Pteronarcyidae) (Knobbed Salmonfly) Stonefly Nymph from the Neversink River (above reservoir) in New York

Collected May 5, 2007 from the Neversink River (above reservoir) in New York

Added by Troutnut on May 10, 2007

Collected May 5, 2007 from the Neversink River (above reservoir) in New York and added by Troutnut on May 10, 2007

Beardius
Posts: 19

Beardius on Aug 1, 2008August 1st, 2008, 8:53 am EDT

Pteronarcys proteus has abdominal knobs but has a squared off pronotum (no projection of knob). It differs from dorsata in having knobs on the abdominal segments. There is a picture of a young Pteronarcys proteus nymph here: http://www.discoverlife.org/mp/20q?search=Pteronarcys+proteus

Pteronarcys comstocki has pronotal projections and a spine-like projection on the anterior mesonotal wingpad. I only found them in one stream (trib of Kettle Creek in central PA) of the dozens I've collected. I have not collected them in MD, but they are reported from WV and PA. There is a photo of an immature nymph here: http://www.discoverlife.org/mp/20o?search=Pteronarcys+comstocki

Pteronarcys biloba has pronotal projections but no spines on the wingpads. P. biloba is common up north (NY, VT, NH, ME, etc.). The photo above is of P. biloba. Nice photo here: http://www.discoverlife.org/mp/20q?search=Pteronarcys+biloba

P. scotti is found in the south (SC,GA, etc.)

I never collected P. dorsata, so I figure it must be in larger or warmer rivers.

GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681

GONZO on Oct 28, 2008October 28th, 2008, 7:51 am EDT

I just noticed that this thread was an answer to questions that I raised some time ago in the related thread. Beardius' comments and the links to photos and identifications done by Donald Chandler (Dsc1) are very helpful.

It is now easier to see that this is biloba and that the other specimen (#490) is probably proteus. In addition to the traits that Beardius mentions, the abdominal knob seems to dramatically diminish or disappear after the 7th segment in proteus, but biloba usually has a prominent knob on segment 8. I really don't know how reliable this is, but it seems to be consistent in all of the specimens I have seen.